I haven't been able to get Syncthing permissions to work. The frustrating thing for me with Android has always been inconsistencies between vendors and weird permissions issues.
It is alright, but SFTP transfer broke for me some time ago. I think it is related to changes in Android, but surprisingly there were not a lot of posts about this issue last I searched. Using Android 13 / Samsung One UI 5.1 with Windows 11.
I use Material Files (from f-droid) as my default file manager, which includes support for mounting FTP, SFTP, SMB, and webdav shares. It doesn't handle the connection getting interrupted very well, so if that happens i have to restart the app. Other than that it's been working great for my SMB share.